The invention relates to a plate heat exchanger and, more particularly, to a plate heat exchanger designed as a heat tube design in the form of a multi-layer expanded partly laminated body with an integrated, fluidically continuous large surface channel structure including a slope, which is at least slight in the installation position of the plate heat exchanger. The slope allows for the gravitational return of the condensate within the channel structure towards the edge of the plate heat exchanger. The channel structure merges in the region of this edge into a condensate-collecting channel extending parallel to the edge. A linear heat-supply element is in heat-conductive contact with the condensate-collecting channel. The heat supply element has the form of at least one of a heating bar and a heating channel.
This type of heat exchanger is known, for example, from German Patent Specification 3,144,089 or other further plate-type heat exchanger publications such as German Offenlegungsschrift 2,730,541, German Offenlegungsschrift 3,041,710, German Patent Specification 3,203,369 or Japanese Preliminary Patent Application 56-130,589, laid open on 13.10.1981.
Plate exchangers or this type, because of their lightweight construction, are readily used in vehicles, for example for omnibus heating. The supply of heat from an external heat source occurs in the region of the longitudinal edge of the plate heat exchanger located geodetically at the bottom in the installation position. The supply of heat comes from a heating bar, heating channel or the like, via which the condensate of the heat-transfer medium collecting in the parallel condensate-collecting channel evaporates and the heat is thus distributed in the large-surface channel structure of the plate heat exchanger. It is important for uniform distribution of the heat over the entire plate of the plate heat exchanger from the marginal edge that the entire length of the condensate-collecting channel be covered with condensate. However, when plate heat exchangers are installed in vehicles, this cannot always be presupposed, because the condensate tends to accumulate at one end of the condensate-collecting channel due to several factors. These factors include the slope of the road on which the vehicle is located - ascending or descending gradient, pronounced transverse inclination of the road profile - or the driving status of the vehicle - transverse acceleration during cornering, longitudinal acceleration or deceleration. This impairs the heating power of the plate heat exchanger and is detrimental to a uniform distribution of the heat over the entire surface.
There is therefore needed a plate heat exchanger of the relevant generic type, wherein despite such unavoidable operating conditions, the best possible heating in terms of transmittable power and of uniform distribution of the heating power over the surface of the plate heat exchanger can nevertheless be guaranteed.
According to the invention, this need is met by means of a plate heat exchanger wherein the condensate-collecting channel is subdivided by run-off obstacles projecting from the underside into a clearance profile of the condensate-collecting channel. The underside is near the edge of the heat exchanger and lower in the direction of gravity. The run-off obstacles take the form of at least one of bottom elevations, bottom corrugations and retaining weirs. The run-off obstacles project into condensate pockets which, despite any longitudinal slope of the condensate-collecting channel, prevent the condensate from flowing off in the longitudinal direction. Because the condensate-collecting channel is subdivided into a plurality of condensate pockets partitioned off from one another by flow obstacles, the condensate running back out of the plate heat exchanger over the surface uniformly, at least in rough approximation, is also retained uniformly in the condensate-collecting channel over the length of the latter. Under the influence of mass or gravity in the longitudinal direction of the condensate-collecting channel, the condensate can at most run within the longitudinal extent of one condensate pocket.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.